XML 108 R94.htm IDEA: XBRL DOCUMENT v3.8.0.1

Restrictions of Dividends & Inter-company Borrowings - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Equity [Abstract]
Dividends may be paid without prior regulatory approval	$ 14.0

X

- Definition

Dividends May Be Paid Without Prior Regulatory Approval

+ References

No definition available.

+ Details

Name:	fmao_DividendsMayBePaidWithoutPriorRegulatoryApproval
Namespace Prefix:	fmao_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- References

No definition available.

+ Details

Name:	us-gaap_EquityAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration